Karlovic was at his Miami home, preparing to travel to an ATP Challenger Tour event at Sarasota in mid-April, when the symptoms first surfaced.

“I woke up and my arm was numb,” the 34-year-old Croatian recalled in Newport. “Then my wife [Alsi] asked me I don’t even remember what. I was slurring, so she called the paramedics.“They gave me IV [therapy] and I felt good. But when they left, I began to vomit a lot and had headaches, so I went to hospital.

“They released me after one hour, but later that evening the numbness and pain returned. I became less and less conscious. I returned to hospital again. I don’t know what happened after that.”Karlovic's condition wasn't diagnosed until three days later and this makes his ATP World Tour return at Newport.

“The doctor’s didn’t really know if I would recover 100 per cent. I was unconscious for a long time. I didn’t know my name or what year it was. I was in a lot of pain. My right arm and my face was numb.“Headaches lasted almost 10 days. I recalled my name after four days and the numbness disappeared after five days.”

Karlovic has since endured a three-month battle for fitness.“The toughest part was fitness, and the fact that I didn’t know if it would happen again because there was still a virus in my head,” he admitted.

“I took to the practice court after one month. Five minutes one week and then every day. I really didn’t know that I would be back, so now it is good feeling because I feel no stress. “It’s like a bonus. Every day now that I’m actually in a match, the atmosphere is like a bonus. I really like it now a lot more.

“I’m not fearful any more. The goal is just to be healthy and here. So it’s fun.”Karlovic made his Grand Slam championship debut at Wimbledon in 2003, when he beat defending champion Lleyton Hewitt in the first round. The former World No. 14 has a 4-3 record in ATP World Tour finals.